INTERFACIAL STRESS TRANSFER MECHANISM IN SIC FIBER-REINFORCED TI MATRIX COMPOSITES

The interfacial shear stress transfer mechanism of fiber-matrix sliding interfaces in SiC fiber-reinforced Ti matrix composites have been studied using both the push-out and pull-out tests. The interfacial shear sliding stress (tau(s)) is expressed as the form of tau(s)=mu(sigma(T)+sigma(R)+sigma(P)), where mu is the coefficient of sliding friction at the sliding interface and sigma(T), sigma(R), sigma(P), respectively, are the thermal residual stress at the fiber radial-direction, the interfacial roughness induced stress and the stress occurred by the Poisson's ratio difference between fiber and matrix. Quantitative evaluations of the mu, sigma(T), sigma(R), sigma(P) and their contribution to the shear sliding stress can become possible by the use of both the push-out and pull-out tests. In case of the SiC(SCS-6) fiber-reinforced commercially-pure Ti matrix composites, tau(s)=30 similar to 50 MPa, mu approximate to 0.2. It was confirmed that the thermal residual stress (sigma(T)), which was introduced at the fiber-matrix interface during the cooling process from the processing temperature, plays a major role in the generation of fiber radial-direction stresses during the shear sliding process of the interface.